Narrative:

Weather had been variable with visibility to 1 br and 200 ovc all morning. The current ATIS was 1 br visibility; with surface visibility 5 miles. Captain was the flying pilot and a CAT3/land 2 approach was briefed. On arrival we were cleared direct [zzzzz intersection]; cross at 3;000 feet or above; cleared ILS. The FMC was programmed with ILS and we were proceeding direct [zzzzz intersection]; which was coded with 190/3;000. The center autopilot was engaged; with LNAV; VNAV; and speed intervene. The MCP had 3;000 feet set in the altitude window. Approaching [zzzzz intersection] the aircraft was descending on path at approximately 210kts and decelerating with flaps 5. During the turn onto final at [zzzzz intersection]; leveling at 3;000; still below the glideslope; the captain armed the approach. Immediately all 3 autopilots engaged; the captain's command bars went full deflection down and the plane violently pitched over. He quickly disconnected the autopilot and stablized the aircraft at approximately 2;500 feet - 2;800 feet on the localizer. Altitude hold was in the FMA and his command bars were pitching for level flight while the first officer (first officer) command bars were pitching for a climb. The GS was still armed with the localizer captured and the aircraft was flying level at approximately 2;500 feet; still below the glideslope. The captain then selected the center autopilot and again all three engaged and the aircraft pitched violently down. He quickly disengaged the autopilot and stabilized the aircraft. 2;000 was set in the MCP altitude window and flch selected. At this point I believe the captain and first officer's flight directors matched. After leveling at 2;000; the decision was made to continue the approach to the CAT1 minimums with the captain manually flying. The aircraft was slowed and configured normally; the glideslope captured at 2;000 feet; a stable approach was flown with the runway in sight at 350 feet and visibility greater than 4 miles.

Related reports:

Google
 

Original NASA ASRS Text

Title: B767 First Officer reported that they were below glideslope; autopilot was engaged; then the aircraft pitched down while coupled with the localizer.

Narrative: Weather had been variable with visibility to 1 BR and 200 OVC all morning. The current ATIS was 1 BR visibility; with surface visibility 5 miles. Captain was the flying pilot and a CAT3/LAND 2 approach was briefed. On arrival we were cleared direct [ZZZZZ Intersection]; cross at 3;000 feet or above; cleared ILS. The FMC was programmed with ILS and we were proceeding direct [ZZZZZ Intersection]; which was coded with 190/3;000. The center autopilot was engaged; with LNAV; VNAV; and Speed Intervene. The MCP had 3;000 feet set in the altitude window. Approaching [ZZZZZ Intersection] the aircraft was descending on path at approximately 210kts and decelerating with flaps 5. During the turn onto final at [ZZZZZ Intersection]; leveling at 3;000; still below the glideslope; the Captain armed the approach. Immediately all 3 autopilots engaged; the captain's command bars went full deflection down and the plane violently pitched over. He quickly disconnected the autopilot and stablized the aircraft at approximately 2;500 feet - 2;800 feet on the localizer. ALT HOLD was in the FMA and his command bars were pitching for level flight while the First Officer (FO) command bars were pitching for a climb. The GS was still armed with the LOC captured and the aircraft was flying level at approximately 2;500 feet; still below the glideslope. The captain then selected the center autopilot and again all three engaged and the aircraft pitched violently down. He quickly disengaged the autopilot and stabilized the aircraft. 2;000 was set in the MCP altitude window and FLCH selected. At this point I believe the Captain and FO's flight directors matched. After leveling at 2;000; the decision was made to continue the approach to the CAT1 minimums with the captain manually flying. The aircraft was slowed and configured normally; the glideslope captured at 2;000 feet; a stable approach was flown with the runway in sight at 350 feet and visibility greater than 4 miles.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.